The present invention relates to new sweetening agents, which are useful in particular for sweetening foods, beverages, confectioneries, pastries, chewing gums, hygiene products, cosmetics, toiletries, pharmaceutical and veterinary products and their equivalents.
U.S. Pat. Nos. 3,725,453 and 3,775,460 have described sweetening agents derived from L-aspartic acid and having the following general formula: ##STR2## wherein X is CF.sub.3 or CCl.sub.3 and wherein Y is 4--CN--C.sub.6 H.sub.4, 4--Cl-6H.sub.4, 4--Br--C.sub.6 H.sub.4, 4F--C.sub.6 H.sub.4 or C.sub.6 H.sub.5.
Tinti et al. have shown that the L-aspartyl residue of the preceding compounds can be replaced, often advantageously, by its higher homolog, the L-glutamyl residue (Naturwissenschaften, 1981, 68, 143).
Tsuchiya et al. have described as sweetening agents, compounds of the formula: ##STR3## ps wherein R.sub.1 and R.sub.3 are H, the halogens, CN, NO.sub.2, R' (R' being a C.sub.1 -C.sub.6 alkyl group), COOR" (R" being a C.sub.1 --C.sub.4 alkyl group), R"CO, halomethyl, R"O, CONHR", SO.sub.2 R" or SOR", wherein R.sub.2 is O or S, and wherein n is 0, 1 or 2 (Japanese Patent No. 86-260052), or of the formula: wherein X is CF.sub.3 CO or CCl.sub.3 CO, wherein Y is CN or NO.sub.2 and wherein n is 1 or 2 (Japanese Patent No. 87-132863), or of the formula: ##STR4## wherein X is CN or NO.sub.2 and wherein n is 1 or 2 (Japanese Patent No. 87-132847), or of the formula: ##STR5## wherein X is CN or NO.sub.2, wherein R is H, a C.sub.1 -C.sub.10 alkyl group or an alkoxy or aryloxy aromatic group and wherein n is 1 or 2 (Japanese Patent No. 87-252754).
The compounds described in the prior art are therefore all N-formyl, N-acyl, N-carbamoyl or N-thiocarbamoyl carbamoyl derivatives of aspartic or glutamic acid alphamonamides. They therefore have a carbonyl group C.dbd.O or a thiocarbonyl group C.dbd.S fixed directly to the alpha-amino group of the aspartyl or glutamyl residue.
The major disadvantage of these N-formyl, N-acyl, N-carbamoyl or N-thiocarbamoyl derivatives for their use as sweetening agents lies in their poor stability in aqueous solution, and thus under the conditions of use that are normal for synthetic sweetening agents, because of the ease of hydrolysis of their N-formyl, N-acyl, N-carbamoyl or N-thiocarbamoyl part, with corresponding reduction of the sweetening power, which circumstance considerably limits their possible industrial application.